METABOLISM IN NEPHRITIS 409 



an arteriosclerotic kidney (brought on by other causes than hypertension) 

 may exist without a concomitant rise in arterial pressure. 



The pathologicophysiological process that is responsible for hyper- 

 tension appears to be an increased vasomotor tone of the smaller arteries. 

 This anomalous condition maintains the blood in the arterial tree under 

 an abnormal degree of tension. The variability of the blood pressure in 

 the hypertensive states, as shown by the reaction to vasodilators and the 

 rapid drop with physical and especially with mental relaxation, indicates 

 that the musculature of the arterial walls is not injured and that the older 

 conception of a fibrosis of the smaller blood vessels is not an adequate ex- 

 planation to account for an increased peripheral resistance in the arterial 

 circulation in most instances. 



The cause for the increased vasomotor tone has not been determined. 

 Insufficient renal function, increased blood volume, increased blood- vis- 

 cosity, hyperadrenalinemia, internal secretions derived from the kidney, 

 intoxication from food products (salt, proteins, purins), and reflexes from 

 partially occluded glomeruli have all been considered in the light of etio- 

 logical factors that might stimulate the tonicity of the arteries, but none 

 of them have up to the present time fulfilled all the requirements neces- 

 sary to make it clear that they are the dominating element in hypertension. 

 There is only one known poison that causes high blood pressure. This 

 is lead. It is probable that there is not one cause but many that may be 

 considered to be responsible for a raised arterial pressure. It would be 

 very strange if such conditions as toxemia of pregnancy, lead poisoning, 

 essential hypertension, etc., should prove to have the same toxic substance 

 to which the increased tonicity of the arterioles could be attributed. 



